The invention relates to an ultrasonic measuring device for determining motion parameters of bodies in motion, in particular path, speed, acceleration, slip or the like. The device comprises two ultrasonic transducers (transmitter and receiver) supported in a housing and composed each of one sound generator and one sound receiver, two vibrating elements and a connecting element securely clamping one of the sound generator and the sound receiver between the vibrating elements. The sound generator includes a quartz crystal, in particular one formed of piezoceramics for a piezo-electric measuring method.
A measuring device with similar general features is known from U.S. Pat. No. 4,506,353. It serves for automatic measurements of speed and path of a mobile element, in particular for the automatic track guiding of a vehicle. For this purpose, there are installed, at the vehicle bottom at a distance corresponding to the vehicle width, two measuring devices each comprising two ultrasonic transmitters and receivers aligned in a longitudinal direction of the vehicle inclined at different angles to the roadway. The ultrasonic transducers are connected to a calculator unit forming control values for the steering drive of the vehicle from the measured values and from the desired values. The measuring device is, however, not described in more detail in its specific construction.
It is known, however, that ultrasonic transducers do transfer sound not only to the air, but also to the housing in which they are accommodates. The sound in the housing is, by a multiple, higher than the sound coming back from the air to the receiver. This leads to faulty results.